Construction before authority to commence?

Hi Forumites
I am building a house in QLD. We signed the final contract and waited for the all the finance to go through with the lender before the builder could commence.
The builder asked not to see the Authority to Commence Construction (ACC) documents before building but gave us a start date when we had shown them our Consumer Constract Schedules (CCS) which showed that finance had been approved.

So the builder went ahead and levelled the block, did pre-slab work and poured the slab.
They now want slab payment but, due to some paperwork not going through yet (FHOG and building boost from QLD), we dont have ACC from the bank and as such we cant pay yet. My thinking was that the builder wanted to start as quick as possible and thought " They'll get ACC by the time the slab is poured because their CCS have been issued"

Has anybody had a similar problem. It looks like most builders wont pick up a shovel without seeing Authority to Commence documents from the lender but ours have already finished the slab and want payment. We dont want to pay interest on the payment for being late.
Any advice? Anyone been in a similar position?